Metabarcoding analysis reveals new metazoan diversity and ecological roles in European coastal samples

Abstract

Marine environments are key to the life on Earth. Thus, understanding the diversity of marine environments is important to human well-being. In this regard, animals are an important component of marine biodiversity, and most of the metazoan phyla have marine representatives. However, we still do not fully understand the diversity of marine micrometazoans and its implications in marine ecology and in animal evolution. To address this, we applied a high*throughput DNA and RNA sequencing (454 pyrosequencing of 18S rRNA gene) approach to characterize the biodiversity of metazoans across different European coastal locations, size fractions and depths. The data show that metazoan reads represent a large percentage of the total eukaryotic reads. Reads from copepods and tunicates are the most abundant ones in the water column, while polychaetes, crustaceans, and platyhelminths appear as the most abundant groups in sediments. Interestingly, our dataset contain a high percentage of novel 18S rRNA metazoan sequences, including a potentially novel environmental metazoan group likely close to tunicates. Moreover, our data suggest that the metazoan sperm might play a relevant role as a source of organic carbon at the pico and naco fraction of the plankton. Overall, our study provides an important dataset, in which to analyze not only abundance and richness patterns of metazoans in marine coastal habitats, but also the possibility to investigate potential novel metazoan lineages that can provide new interesting phylogenetic information.